This invention relates to devices for deploying and securing the ends of bypass grafts designed to provide a fluid flow passage between at least two host vessel regions (or other tubular structure regions). More particularly, the invention relates to bypass grafts that are secured at target host vessel locations, thereby producing a fluid flow passage from the first host vessel location through the bypass graft and to the second host vessel location. The bypass grafts and deployment systems of the invention do not require stopping or re-routing blood flow to perform an anastomosis between a bypass graft and a host vessel. Accordingly, this invention describes sutureless anastomosis systems that do not require cardiopulmonary bypass support when treating coronary artery disease.
Current techniques for producing anastomoses during coronary artery bypass grafting procedures involve placing the patient on cardiopulmonary bypass support, arresting the heart, and interrupting blood flow to suture, clip, or staple a bypass graft to the coronary artery and aorta; cardiopulmonary bypass support is associated with substantial morbidity and mortality. The embodiments of the invention position and secure bypass grafts at host vessel locations without having to stop or re-route blood flow. Accordingly, the embodiments of the invention do not require cardiopulmonary bypass support and arresting the heart while producing anastomoses to the coronary arteries. In addition, the embodiments of the invention mitigate risks associated with suturing, clipping, or stapling the bypass graft to the host vessel(s); namely, bleeding at the attachment sites and collapsing of the vessel around the incision point.
The invention addresses vascular bypass graft treatment regimens requiring end-end anastomoses and end-side anastomoses to attach bypass grafts to host vessels. The scope of the invention includes improvements to the systems used to position and secure bypass grafts for treating vascular diseases such as atherosclerosis, arteriosclerosis, fistulas, aneurysms, occlusions, and thromboses. The improvements to the bypass grafts and delivery systems of the invention also aid in attaching the ends of ligated vessels, replacing vessels harvested for bypass grafting procedures (e.g. radial artery), and re-establishing blood flow to branching vessels which would otherwise be occluded during surgical grafting procedures (e.g., the renal arteries during abdominal aortic aneurysm treatment). In addition, the invention addresses other applications such as, but not limited to, producing arterial-to-venous shunts for hemodialysis patients, bypassing lesions and scar tissue located in the fallopian tubes causing infertility, attaching the ureter to the kidneys during transplants, and treating gastrointestinal defects (e.g. occlusions, ulcers, obstructions, etc.).
Stenosed blood vessels cause ischemia potentially leading to tissue infarction. Conventional techniques to treat partially or completely occluded vessels include balloon angioplasty, stent deployment, atherectomy, and bypass grafting.
Coronary artery bypass grafting (CABG) procedures to treat coronary artery disease have traditionally been performed through a thoracotomy with the patient placed on cardiopulmonary bypass support and using cardioplegia to induce cardiac arrest. Cardiac protection is required when performing bypass grafting procedures associated with prolonged ischemia times. Current bypass grafting procedures involve interrupting blood flow to suture or staple the bypass graft to the host vessel wall and create the anastomoses. When suturing, clipping, or stapling the bypass graft to the host vessel wall, a large incision is made through the host vessel and the bypass graft is sewn to the host vessel wall such that the endothelial layers of the bypass graft and vessel face each other. Bypass graft intima-to-host vessel intima apposition reduces the incidence of thrombosis associated with biological reactions that result from blood contacting the epithelial layer of a harvested bypass graft. This is especially relevant when using harvested vessels that have a small inner diameter (e.g., xe2x89xa62 mm).
Less invasive attempts for positioning bypass grafts at target vessel locations have used small ports to access the anatomy. These approaches use endoscopic visualization and modified surgical instruments (e.g., clamps, scissors, scalpels, etc.) to position and suture the ends of the bypass graft at the host vessel locations. Attempts to eliminate the need for cardiopulmonary bypass support while performing CABG procedures have benefited from devices that stabilize the motion of the heart, retractors that temporarily occlude blood flow through the host vessel, and shunts that re-route the blood flow around the anastomosis site. Stabilizers and retractors still require significant time and complexity to expose the host vessel and suture the bypass graft to the host vessel wall. Shunts not only add to the complexity and length of the procedure, but they require a secondary procedure to close the insertion sites proximal and distal to the anastomosis site.
Attempts to automate formation of sutureless anastomoses have culminated into mechanical stapling devices. Mechanical stapling devices have been proposed for creating end-end anastomoses between the open ends of transected vessels. Berggren et al. propose an automatic stapling device for use in microsurgery (U.S. Pat. Nos. 4,607,637, 4,624,257, 4,917,090, and 4,917,091). This stapling device has mating sections containing pins that are locked together after the vessel ends are fed through lumens in the sections and everted over the pins. This stapling device maintains intima-to-intima apposition for the severed vessel ends but has a large profile and requires impaling the everted vessel wall with the pins. Sakura describes a mechanical end-end stapling device designed to reattach severed vessels (U.S. Pat. No. 4,214,587). This device has a wire wound into a zigzag pattern to permit radial motion and contains pins bonded to the wire that are used to penetrate tissue. One vessel end is everted over and secured to the pins of the end-end stapling device, and the other vessel end is advanced over the end-end stapling device and attached with the pins. Sauer et al. proposes another mechanical end-end device that inserts mating pieces into each open end of a severed vessel (U.S. Pat. No. 5,503,635). Once positioned, the mating pieces snap together to bond the vessel ends. These end-end devices are amenable to reattaching severed vessels but are not suitable to producing end-end anastomoses between a bypass graft and an intact vessel, especially when exposure to the vessel is limited.
Mechanical stapling devices have also been proposed for end-side anastomoses. These devices are designed to insert bypass grafts, attached to the mechanical devices, into the host vessel through a large incision and secure the bypass graft to the host vessel. Kaster describes vascular stapling apparatus for producing end-side anastomoses (U.S. Pat. Nos. 4,366,819, 4,368,736, and 5,234,447). Kaster""s end-side apparatus is inserted through a large incision in the host vessel wall. The apparatus has an inner flange that is placed against the interior of the vessel wall and a locking ring that is affixed to the fitting. This locking ring contains spikes that penetrate into the vessel thereby securing the apparatus to the vessel wall. The bypass graft is itself secured to the apparatus in the everted or non-everted position through the use of spikes incorporated in the apparatus design.
U.S. Surgical has developed automatic clip appliers that replace suture stitches with clips (U.S. Pat. Nos. 5,868,761, 5,868,759, and 5,779,718). These clipping devices have been demonstrated to reduce the time required when producing the anastomosis but still involve making a large incision through the host vessel wall. As a result, blood flow through the host vessel must be interrupted while creating the anastomoses.
Gifford et al. provides end-side stapling devices (U.S. Pat. No. 5,695,504) that secure harvested vessels to host vessel walls maintaining intima-to-intima apposition. This stapling device is also inserted through a large incision in the host vessel wall and uses staples incorporated in the device to penetrate into tissue and secure the bypass graft to the host vessel.
Walsh et al. proposes a similar end-side stapling device (U.S. Pat. Nos. 4,657,019, 4,787,386, and 4,917,087). This end-side device has a ring with tissue-piercing pins. The bypass graft is everted over the ring; then, the pins penetrate the bypass graft thereby securing the bypass graft to the ring. The ring is inserted through a large incision created in the host vessel wall and the tissue piercing pins are used to puncture the host vessel wall. A clip is then used to prevent dislodgment of the ring relative to the host vessel.
The previously described end-side stapling devices require insertion through a large incision, which dictates that blood flow through the host vessel must be interrupted during the process. Even though these and other clipping and stapling end-side anastomotic devices have been designed to decrease the time required to create the anastomosis, interruption of blood flow through the host vessel increases the morbidity and mortality of bypass grafting procedures, especially during beating heart CABG procedures. A recent experimental study of the U.S. Surgical One-Shot anastomotic clip applier observed abrupt ventricular fibrillation during four of fourteen internal thoracic artery to left anterior descending artery anastomoses in part due to coronary occlusion times exceeding 90 seconds (Heijmen, et al. xe2x80x9cA Novel One-Shot Anastomotic Stapler Prototype for Coronary Bypass Grafting on the Beating Heart: Feasibility in the Pigxe2x80x9d J Thorac Cardiovasc Surg. 117:117-25; 1999).
A need thus exists for bypass grafts and delivery systems that are capable of quickly producing an anastomosis between a bypass graft and a host vessel wall without having to stop or re-route blood flow. These anastomoses must withstand the pressure exerted by the pumping heart and ensure blood does not leak from the anastomoses into the thoracic cavity, abdominal cavity, or other region exterior to the vessel wall.
The embodiments of the present invention provide improvements to sutureless anastomosis systems that enable a physician to quickly and accurately secure a bypass graft to a host vessel or other tubular body structure. In addition, the invention adapts the sutureless anastomosis systems to applications involving robotic surgery and minimally invasive surgical approaches that involve a thoracostomy. The delivery systems of the invention do not require stopping or re-routing blood flow while producing the anastomosis; current techniques require interrupting blood flow to suture, clip, or staple a bypass graft to the host vessel wall.
The fittings of the invention are intended to secure biological bypass grafts, obtained by harvesting vessels from the patient or another donor patient, or synthetic bypass graft materials, to a patient""s host vessel. When using harvested vessels, the fitting embodiments must accommodate a variety of harvested vessel sizes and wall thicknesses. When using synthetic bypass graft materials, the fittings may be incorporated in the bypass graft design to eliminate the step of attaching the bypass graft to the fitting prior to deploying the bypass graft and fitting.
One aspect of the invention provides additional fitting embodiments designed to compress into a reduced diameter while attaching the bypass graft to the fitting and/or deploying the fitting through the delivery system. Once deployed, the compressible fittings of the invention expand towards their preformed geometry such that they exert radial force at the vessel attachment sites; this helps maintain the patency of the anastomosis.
Another aspect of the invention provides additional angled fittings designed to produce anastomoses between bypass grafts and host vessels such that the angle between the bypass graft and the host vessel reduces turbulent flow near the anastomosis. The angled fittings may also be designed compressible.
A further aspect of the invention involves loading sheaths to facilitate securing the bypass graft to the fittings of the invention, and inserting the bypass graft and fitting combination through the delivery system. The loading sheath also protects the bypass graft and fitting combination during insertion through the delivery sheath. One loading sheath embodiment enables compressing the end-side fitting into a reduced diameter to facilitate advancing the bypass graft over the fitting base prior to securing the bypass graft to the fitting using a retaining ring or other compression device.
The single motion delivery system of the invention enables inserting the fitting and bypass graft into the host vessel without having to interrupt blood flow through the host vessel. The single motion delivery system embodiment combines the tear-away sheath, plunger, dilating mechanism, and perforating mechanism described in U.S. patent application Ser. No. 09/329,503 into a single tool designed to deploy the fitting and bypass graft combination through the host vessel wall at the desired anastomosis site. After securing the bypass graft to the host vessel, components of delivery system still residing around the attached bypass graft are configured to split or expand to form a gap so the entire delivery system may be removed from around the bypass graft. This facilitates attaching both ends of the bypass graft using the delivery system of the invention and removing the delivery system from around the intact bypass graft. The delivery system also protects the bypass graft during insertion through an opening into the host vessel.
Further features and advantages of the inventions will be elaborated in the detailed description and accompanying drawings.